withastro/astro · warning

[${id}] Astro now supports MDX! Support for components in ".

Error message

[${id}] Astro now supports MDX! Support for components in ".md" (or alternative extensions like ".markdown") files using the "setup" frontmatter is no longer enabled by default. Migrate this file to MDX.

What it means

The markdown plugin inspects frontmatter while transforming a .md file: if a `setup` key exists it warns that the legacy feature — embedding components/scripts in markdown via setup frontmatter — is no longer enabled by default, and directs you to MDX, which supports components natively. The file still compiles as plain markdown.

Source

Thrown at packages/astro/src/vite-plugin-markdown/index.ts:125

				} = renderResult.metadata;

				// Add default charset for markdown pages
				const isMarkdownPage = isPage(fileURL, settings);
				const charset = isMarkdownPage ? '<meta charset="utf-8">' : '';

				// Resolve all the extracted images from the content
				const localImagePaths: MarkdownImagePath[] = [];
				for (const imagePath of rawLocalImagePaths) {
					localImagePaths.push({
						raw: imagePath,
						safeName: shorthash(imagePath),
					});
				}

				const { layout } = frontmatter;

				if (frontmatter.setup) {
					logger.warn(
						'markdown',
						`[${id}] Astro now supports MDX! Support for components in ".md" (or alternative extensions like ".markdown") files using the "setup" frontmatter is no longer enabled by default. Migrate this file to MDX.`,
					);
				}

				const code = `
				import { unescapeHTML, spreadAttributes, createComponent, render, renderComponent, maybeRenderHead } from ${JSON.stringify(
					astroServerRuntimeModulePath,
				)};
				import { AstroError, AstroErrorData } from ${JSON.stringify(astroErrorModulePath)};
				${layout ? `import Layout from ${JSON.stringify(layout)};` : ''}

				${
					// Only include the code relevant to `astro:assets` if there's images in the file
					localImagePaths.length > 0 || remoteImagePaths.length > 0
						? getMarkdownCodeForImages(localImagePaths, remoteImagePaths, html)
						: `const html = () => ${JSON.stringify(html)};`
				}

View on GitHub (pinned to 52e6c34790)

Solutions

1. Rename the file from .md to .mdx and replace the setup frontmatter with real MDX imports/exports at the top of the file
2. Remove the setup frontmatter entirely if it is unused
3. Audit content collections for schema changes once files become .mdx

Example fix

# before  src/content/blog/post.md
---
setup: |
  import Banner from '../../components/Banner.astro';
---
<Banner />{/* rendered only with legacy .md component support */}

# after  src/content/blog/post.mdx
import Banner from '../../components/Banner.astro';

<Banner />

# CI gate: no legacy `setup` frontmatter left in markdown files
grep -rl --include='*.md' -E '^setup:' src/ && { echo 'migrate .md setup frontmatter to .mdx'; exit 1; } || true

When it happens

Trigger: A .md (or .markdown) page/content file whose YAML frontmatter contains `setup:`, processed during dev or build. The plugin keys the warning off frontmatter.setup regardless of whether the setup code referenced Astro components.

Common situations: Projects dating to Astro 1/2 that used component-enhanced markdown; content authors copying old templates; after an upgrade, components in .md files silently stop rendering because the legacy pipeline is gone.

Related errors

• [MDX] A remark or rehype plugin attempted to inject invalid
• ${colors.bold(plugin)} not applied.
• To inherit Markdown plugins in MDX, please use explicit impo
• [MDX] A Sätteri plugin attempted to inject invalid frontmatt
• InvalidFrontmatterInjectionError

AI-assisted analysis of withastro/astro@52e6c34790 (2026-08-18). Data as JSON: /api/errors/7e1a735438ed5717. Report an issue: GitHub.